"If you are a user of cocaine, you should be aware that some of the cocaine is not clean and can have other agents that can cause you to have a low white-cell count or skin tissue death," said Dr. Ghinwa Dumyati, an associate professor of medicine at the University of Rochester and an epidemiologist for the Monroe County Health Department in New York.

In a report in the June 1 issue of Annals of Internal Medicine, Dumyati and doctors from the University of Rochester Medical Center discuss two cases involving women with a history of cocaine use who came to the hospital for help when they noticed purplish plaques on their cheeks, earlobes, legs, thighs and buttocks.

Their profiles were typical of toxicity with levamisole, the doctors reported. The medication is a veterinary anti-worming agent, approved for use in cattle, sheep and pigs. It was once used to treat cancer, autoimmune diseases and kidney problems in humans, Dumyati said. It's no longer approved for use in people in the United States, she said, because of adverse side effects.

But it's often used to cut cocaine, before distribution to the user, she said. "Almost 80 percent of the cocaine coming into this country has levamisole mixed in," Dumyati said.

Exactly why is not known, she said. Some say it might enhance the effects of the drug, which include a euphoric mood or ''high" and a boost in energy. It also might be used to stretch the drug and increase profits.

"The person using cocaine would not know this [levamisole] is in it," Dumyati said.

In the new report, the doctors concluded, based on the women's symptoms, that cocaine laced with levamisole cannot only cause problems with white blood cells -- a problem previously reported -- but also death of the skin's outer layer. They said that physicians should suspect cocaine abuse when they see patients with skin lesions caused by tissue death.

"The drug may induce an immunological reaction producing inflammation or vasculitis, an inflammation inside the small blood vessels," Dumyati said in explaining the link to tissue death. "The result can be the death of the epidermis or outer layer of skin."

But that's not all that's bad about levamisole. "It has other side effects," she said. "It has effects on bone marrow function. There can be a drop in the white blood cell count."

The U.S. Centers for Disease Control and Prevention reported in late 2009 on a cluster of cases of problems with white blood cell counts linked to cocaine use. Called agranulocytosis, the condition occurs when bone marrow fails to make enough white blood cells.

The report noted that levamisole was found in some of the people with agranulocytosis and cocaine exposure.

But the reports of tissue death associated with contaminated cocaine are newer, said Dr. Kurt Nolte, a pathology professor at the University of New Mexico and one of the authors of the CDC report. "Tissue death has been associated with levamisole in a clinical context," when the drug was used therapeutically, he said. "I've not seen any cocaine users with this."

But it's not a surprise, given the amount of cocaine that has been laced with the medication, said Dr. Juliet VanEenwyk, an epidemiologist with the Washington State Department of Health, who also contributed information to the CDC report.

"The increase [in cocaine containing levamisole] has been really rapid," she said. Until a few years ago, she said, probably less than 10 percent of cocaine supplies had it. Now, experts suspect that 80 percent do.

Dumyati said that the skin problem is treatable, but "if you stop using cocaine, most of the cases would get better."

Agranulocytosis, on the other hand, is a serious illness that requires hospitalization for treatment, according to the U.S. Department of Health and Human Services.

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